Effective, natural contraception? Yes and no
Often referred to as natural birth control methods, approaches based on fertility awareness are perceived as ineffective. What is it really ? The Rumor Detector checked.
According to the Office of Population and Reproductive Health of the United States, which falls under the Agency for International Development, the so-called natural strategies should not be considered traditional methods, but rather modern methods of contraception, since they are based on mechanisms well understood by scientists.
For example, in a study published in 1995, American researchers observed that for a baby to be conceived, sexual intercourse must take place during the period of 6 consecutive days that ends with ovulation. This period is called the “fertility window”. Fertility awareness methods are based on the idea that by recognizing the time of ovulation, one can identify the days when unprotected sex should be avoided.
Signs to watch out for
However, there is a downside: how to predict ovulation? In a knowledge brief published in May 2022, Dr. Marguerite Duane, who teaches Introduction to Natural Contraception Methods at Georgetown University, USA, explains that the female reproductive system produces observable physiological changes throughout of the menstrual cycle.
In an article published in December 2019, American researchers Rebecca Simmons and Victoria Jennings list the four main signs used in methods based on fertility awareness.
- Basal temperature: It is the body temperature at rest. It increases by about 0.3oC just after ovulation due to the increase in progesterone.
- Cervical secretions: This involves observing the presence and appearance of mucus that drains from the cervix. Two to three days before ovulation, these secretions become more abundant, clear and elastic.
- The length of the menstrual cycle: In women who have a cycle of 26 at 32 days, the fertile window is usually between day 8 and day 19.
- Hormones present in urine: Detection kits can recognize the presence of luteinizing hormone (LH), which peaks at the time of ovulation.
However, according to Marguerite Duane, these signs are more appropriate to identify the end of the fertile period, rather than its beginning. Added to this is the fact that ovulation varies from woman to woman, insist Rebecca Simmons and Victoria Jennings. The different methods based on fertility awareness actually offer a fertility window of more than 6 days to reduce the risk of an unwanted pregnancy.
Natural contraception: multiple strategies
Some approaches use only one sign. This is particularly the case with the Billings method (analysis of cervical secretions) or the calendar method. According to Marguerite Duane, strategies based solely on the length of the menstrual cycle are generally not precise enough.
Others use several physiological signs. This is the case of the Marquette method and the symptothermal method. This information must then be recorded in graphs, either on paper or in an application, recommends Marguerite Duane.
In a 2019 article, Rachel Urrutia and Chelsea Polis, two American researchers who are interested in contraception, concluded that only 14 methods based on fertility awareness had been the subject of clinical studies. The many other variations offered to women have not been tested. In addition, the studies would be few in number and generally of low quality, underlined a year earlier by American researchers who carried out a systematic review of the question.
In addition, a study published in 2016 on the performance of applications marketed to prevent pregnancies noted that they had not all been developed based on the principles of fertility awareness. They often used their own algorithm, without having been evaluated in a published and peer-reviewed study.
Researchers Rachel Urrutia and Chelsea Polis explain that when the time comes to study or compare the effectiveness of contraceptive methods, researchers generally rely on two separate data: the failure rate in perfect use and the rate of failure in typical use. The latter takes into account the fact that a normal person does not always follow the instructions to the letter.
Result, describes Marguerite Duane, these methods have an average failure rate of less than 5% in perfect use. In other words, they make it possible to identify the fertile window with fairly high precision, note Rebecca Simmons and Victoria Jennings.
The problem, however, is that many people don't use them perfectly, and these methods are very susceptible to inconsistent use. Thus, if we measure typical use instead, the average failure rate rises to 15% and can even vary between 2 and 23%, wrote in 2020 Charisse Loder and Jen Villavicencio, two American doctors specializing in contraception .
In comparison, the birth control pill, in typical use, has a failure rate of 7%, contraceptive implants 0.1%, hormonal IUDs 0.8% and the male condom 13%, according to US data. recent studies.
Even failure rates in typical use probably underestimate the risk of pregnancy, note Rachel Urrutia and Chelsea Polis, since these results were obtained from studies where participants were usually highly motivated and therefore more likely to follow protocol well.
Difficult to use
Urrutia and Polis point out that methods based on fertility awareness require a greater commitment on the part of the user. In addition, as the couple must modify their sexual habits during the fertile window, the motivation to avoid pregnancy can influence the effectiveness of the method, adds Marguerite Duane. Couples who choose to use these methods should also receive clear instructions from a medical professional.
One more caveat: these methods are more appropriate for women with regular cycles, point out Charisse Loder and Jen Villavicencio. Finally, certain health problems can complicate the interpretation of biological signs, add Rebecca Simmons and Victoria Jennings.
It is no coincidence, according to Loder and Villavicencio, that many women abandon these methods after less than a year of use. An American study published in 2018 observed that so-called natural methods of contraception were used by only 2 to 3% of women who used a method of contraception in 2014.
Some so-called natural birth control methods are better than others at accurately identifying fertile days in the menstrual cycle. But the complexity of their use diminishes their effectiveness.